Grinding machine



March 1944- w. F. FRASER GRINDING MACHIDUE:

Original Filed Aug. 29, 1940 5 Sheets-Sheet l 0 Ma M a O liiniiilm n 3km March 28, 1944. w, FRASER GRINDING MACHINE Original Filed Aug 29,1940 I -5 Sheets-Sheet 2 March 1944- w. F. FRASER I GRINDING MACHINE 5Sheets-Sheet 5' Original Filed Aug. 29, 1940 28, 1944. w. F. FRASERGRINDING MACHINE Original Filed Aug. 29, 1940 5 Sheets-Sheet 5 .Ill illln-E v Inl enfor:

Patented Mar. 28, 1944 UNITED STATES PATENT GFF IC'E r 2,345,189.GRINDING MACHINE WarrenKF. Eraser, Westboro, Mass Original applicationAugust 29, 1940, Serial No.

Divided and this-application March 1942, Serial No. 436,130

1 Claim.

This invention relates tosurface: grinding machines and is moreespeciallyconcerned with those factors affecting the accuracy ofthesurface produced by the grinding operation.

A typical machine of'this type includes a work support, a wheel headcarrying-a revolving grinding wheel, and means supporting saidhead forreciprocating'mcvement to carry said wheel'backward and forward acrossthesur-faceof the work. While machines of this typ are old and wellknown and they have been widely used; they always have a tendency toproduce a wavy surface in the work. In some cases, also, there is n.discernible difference in the cut produced on the forward stroke ascompared'with that on the return stroke. Of course any such irregularityin the surface is noticeable only upon very careful inspection, butnevertheless machine manufacturers are quite conscious. of this fault.This effect often is referred to as chatter, although no audible chatteris discernible, and. it isdue to some relative vibration between the,Work support and the Wheel spindle. While it isnot customarilytroublesome it does become important when extreme accuracy, say down toa fraction of one ten-thousandth of. an inch; and fineness of finishare-required.

The present invention is especially concerned with these considerations,and it aims to im-l prove the organization of machines of this type witha view to minimizing these difficulties.

The nature of the invention will be readily understood from thefollowing description when read in connection with the accompanyingdrawings, and the novel features will be particularly pointed out in theappended claim In the drawings,

Figure 1 is a side elevation of a surface grinder embodying features ofthis invention;

Fig. 2 is an elevation of the opposite side of the machine from thatshown in Fig. 1;

Fig. 3 is a rear elevation of the machine with parts broken away;

Fig. 4 is a vertical; sectional view through the wheel head and adjacentparts, the section being taken approximately inthe vertical plane of:the axis of the wheelspindle and Fig. 5 is a vertical, sectional viewapproximately on the line 5-5ofFig. l. 7

Referring first to Figs. 1- and 2, the machine there shown includes arotary chuck 2 partlyenclosed in a casing I, this chuck being mounted torevolve around a vertical axis, together with a wheel head 3, and agrinding wheel mounted in said head. So far as this general organizationis concerned; the machine is likethcse common. ly used heretofore.

As better shown in Figs. 3 and 5", the Wheel head 3 is provided withguiding surfaces designed to slide horizontally on ways: 5 and B whichare formed in the upper part of the section I of the machine frameorbase. In the preferred ernbcdiment of the invention thewheel' head isreciprocated backward and forward in these ways to carry-the wheelacross the surface-of the work by means of an hydraulic mechanismincluding a cylinder 8. A unique feature of the invention resides in thefact that the axis of'this cylinder is located approximately in the samehorizontal plane with theways 5 and 5. This relationship isbetter-illustrated in Fig. 5'. Consequently; the thrust exerted on thehead tov move it in either direction is in the plane of the frictionalresistance which this thrust must overcome. Preferably this thrust isexerted approximately midway betweenthe two longitudinal. pairs: ofsurfaces between which this frictional resistance is generated.

It will further be seen from an inspection of Figs. 3 and ithat thewheel? spindle Ill. ismounn ed in axial alignment with the cylinder 8 sothat it also is in approximately the same horizontal plane with the ways5 and 6. Atv its rearward end this spindle is belt-connectedito thedriving shaft of anelectric motor lz whi'chismounted on. the Wheel headdirectly above the cylinder and the axis of its shaft preferably is insubstantially the vertical plane passing through the axes of the spindleIll and cylinder 8.

By making the base section 1 heavy, stiff and rigid and supporting thecylinder, and Preferably also the spindle, approximately in thehorizontal plane of the ways, any leverage effect of those forcestending to produce relative vibration betweenthe wheel and the work is.reduced? to a minimum, with a consequent substantial improvementin theoperating characteristics of the machine. The fact, also, that thisarrangement permits the lowering of the center of gravity ofthe wheelhead to a point close to the: horizontal plane of the ways, as will beevident from an inspection or Fig. 5, assists. in producing thisdesirable'result.

Afurther'novel feature contributing to this result is the fact that theframe or base of the machine is made in two sections, asillustrated'ineach of Figs. '1 to 5, inclusive. The lower section l3,orthe main part ofthebase, consists-of a heavy, stiff casting designed"to rest on the floor and to support and house certain of the-- drivingmechanisms, as is customary in machines of this type. This section isprovided with a vertical dove-tail guide 55 on which the bracket 53 thatsupports the chuck 2 and the driving and adjusting means therefor ismounted for vertical adjustment.

The upper section 1 also consists of a heavy, stiff castingreinforcedboth longitudinally and transverselyby ribs, shown at l4. andlin, Figs. 4 and 5, integral with the sides and horizontal bottom web ofthe casting. These two sections are,

secured together at three points only forming the corners of a triangle.

machine frame near opposite edges thereof, while the third point I9 isat the rear of the frame Two of these points, I1 and [8, Fig. 5, arelocated at the front of the the oil or other liquid used in thehydraulic .mechanism for reciprocating the wheel head inand is locatedapproximately midway between the vertical planes of the ways 5 and 6.

These connections of the upper frame section to the lower section mayconveniently consist simply of bolts passing loosely through thelowermost web or plate of the upper section and threaded into the metalof the lower section. Each of these bolts extends through a bearingarea, preferably includinga series of spacing washers or shims. Such athree-point support for the upper frame section reduces the distortingeffects of expansion and contraction of the base on the upper framesection and the ways which area part of it. It isolates the uppersectionfrom the lower and thus renders the former substantially unaffected bychanges in the latter, such'as those due to mechanical stress set up inor through the chuck slide 56,,or stresses caused by forces inthecastings, or by the driv- .ing mechanism in the lower section, and whichstresses and strains would be likely to spring or warp the ways 5 and 6sufficiently to cause chatter or vibrations of the character above de--scribed.

This construction also permits the designing of the upper frame sectionso that it is of a more nearly uniform thickness, is less liable towarp, and its-tendency to change dimensions in ways that will affect theoperation of the wheel on the work are reduced. This result is furtheraided by the fact that the motor is located overhead and moves with thewheel head so that no slots are made through the main plates of eitherbase sectiomas is'customarily required for the passage ofthe drivingbelt.

The arrangement for reciprocating the wheel head further is unique inthat the cylinder 8 is fastened securely to the wheel head and movestherewith, the piston being stationary. As best shown'in-Figs. 1, land5, the cylinder fits snugly into axbore formed for it in the frameportion of the wheel head,'and a circumferential flange 2|, integralwith the cylinder, is secured: to the adjacent portion of the wheel headframe by bolts or screws, such as those shown at 22;.

Fig. 5. The oil or other fluid used in thismechanismis conducted to: andfrom the cylin-' and from the cylinder 4 is produced in properlytimedrelationship to the cycles of operations of the machine. So far asthis supply and the,

valve. mechanism are concerned, they may be.

like those heretofore used in hydraulically opcludes a rotary pump 26drawing oil through the pipe 21' from the supply tank 30 and forcing itthrough the pipe 28 into the valve mechanism 25 and thence into thecylinder 8 when allowed to do'so bythevalve mechanism. The exhaust oilis returned from the valve mechanism to the tank through the pipe 3|.

For the purpose of driving both this pump and also the rotary chuck 2,an electric motor 32, a

Fig. 3, is mounted on the machine frame at the rearward end thereofwhere it drives a variable speed mechansm mounted in the housing 33. Asbetter shown in Fig. 1, the particular variable speed mechanism used inthis machine is of the Reeves type including two pulleys, each pulleyincluding two reversely positioned cones which are adjustable toward andfrom each other. The pulleys are connected by a belt of frusto-conicalform in cross-section so that the operating ratio may be varied througha wide range by the adjustment of these conical pulley sections towardand from each other. In Fig. 1, this variable speed mechanism isindicated at 34. The adjusting shaft for the mechanism is shown at35,and the power output shaft is shown in Figs. 2 and 3 at 36. A long belt31, Fig. 2, connects the pulley 38 on the shaft 36 with a driven pulley40 on a jack shaft 4|, mounted in the chuck bracket 4?, and this beltnot only drives that pulley but also the pulley 43 of the pump 26, anidler 44 resting on the belt between the pulley 43 and 38 to keep ittaut. At the front of the machine the pulley 40 is belted to anotherpulley 45 on the driving shaft 46 for the chuck 2, this chuck drive, forexample, being like that shown in my patent above referred to. In orderto provide for the convenient adjustment of the variable speed drivingmechanism 34, the screw shaft or adjusting shaft 35 of this mechanism isconnected by means of a sprocket and chain drive with a hand wheel 41,Fig. 1, mounted on the side of the'framaso that by turning this wheelthe driving speedof both the chuck 2 and the pump 43 can be increased orreduced, as desired. An indicating disk 48 preferably is geared to thehand wheel 41 andis graduated in any convenient manner as, for example,to indicate chuck speeds.

With this arrangement the speeds of both the wheel head and the chuckcan be varied through a wide range. In addition, it also avoids thenecessity for operating the pump continuously at the maximum outputwhich it must'be expected to deliver under some conditions. The normalrelationship between the pump speed and the chuck speed is such that thewheel head is trav: ersed at the maximum speed required for thatparticular work'speed. -When it is desired to reduce the speed oftraverse of the wheel. that result. isaccomplished by adjustment of athrottle valve which is actuated by turning the knob 50 attached to ashaft5l extending through the machine and having on the back thereof alever 52 connected through a link 53 to a similar lever 54 on anextension of the throttle 55.

The long, horizontal belt 31, Fig. 2, accommodates the verticaladjustment of the chuck 2 without afl'ecting the driving connectionsbetween the chuck and the variable speed mechanism.

While I have herein shown and described a preferred embodiment of myinvention, it will be evident that the invention may be embodied inother forms without departing from the spirit or scope thereof.

This application is a division of my copending application Serial No.354,634, filed August 29, 1940, and is limited to that feature of themachine comprising the construction of the base in upper and lowersections and the means for securing these sections together at aplurality of bearing points, preferably three, with the sections spacedslightly apart.

Having thus described my invention, what I desire to claim as new is:

In a grinding machine, the combination of a grinding wheel, a worksupport, a wheel head including a horizontal spindle on which said wheelis mounted and a slide supporting said spindle, a machine basecomprising heavy, stiif upper and lower frame sections, a bracket onwhich said Work support is mounted, vertical guides rigid with saidlower frame section on which said bracket is supported for verticaladjustment, said upper section having horizontal ways on which saidwheel head slide is mounted for reciprocating movement toward and fromsaid work support and including a horizontal bottom web and stiffeningribs located between the sides of said upper section and integral withsaid sides and bottom web and extending both longitudinally andtransversely of said upper section, means securing said sectionstogether at three supporting points only located at the corners of atriangle and isolating said upper section from said lower section exceptat said points, two of said points being located at one end portion ofthe frame and spaced widely apart, while the third point ofsupport is atthe opposite end portion of the frame and is located substantiallymidway between the vertical planes of said ways.

WARREN F. FRASER.

